#region Copyright (c) 2003 - 2008, Andreas Mueller
/////////////////////////////////////////////////////////////////////////////////////////
// 
// Copyright (c) 2003 - 2008, Andreas Mueller.
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// which accompanies this distribution, and is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// Contributors:
//    Andreas Mueller - initial API and implementation
//
// 
// This software is derived from software bearing the following
// restrictions:
// 
// Copyright (c) 1994
// Hewlett-Packard Company
// 
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation.  Hewlett-Packard Company makes no
// representations about the suitability of this software for any
// purpose.  It is provided "as is" without express or implied warranty.
// 
// 
// Copyright (c) 1996,1997
// Silicon Graphics Computer Systems, Inc.
// 
// Permission to use, copy, modify, distribute and sell this software
// and its documentation for any purpose is hereby granted without fee,
// provided that the above copyright notice appear in all copies and
// that both that copyright notice and this permission notice appear
// in supporting documentation.  Silicon Graphics makes no
// representations about the suitability of this software for any
// purpose.  It is provided "as is" without express or implied warranty.
// 
// 
// (C) Copyright Nicolai M. Josuttis 1999.
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
// 
/////////////////////////////////////////////////////////////////////////////////////////
#endregion
using NUnit.Framework;
using NUnit.Framework.SyntaxHelpers;

namespace NStl.NUnit.Support
{
    /// <summary>
    /// Basic test fixture for objects that override Equals and
    /// GetHashcode.
    /// </summary>
    public abstract class EquivalentObjectFixture<T>
    {
        /// <summary>
        /// When implemented, it creates a new object under test. The
        /// returned objects will be equivalent to each other
        /// </summary>
        /// <returns></returns>
        protected abstract T CreateFirstObject();
        /// <summary>
        /// When implemented, it creates a new object under test. The
        /// returned objects will be equivalent to each other an will be
        /// not equvalent to the objects of CreateFirstObject.
        /// </summary>
        /// <returns></returns>
        protected abstract T CreateSecondObject();
        [Test]
        public void CreateCreatesUniqueInstances()
        {
            Assert.That(CreateFirstObject(), Is.Not.SameAs(CreateFirstObject()));
        }
        [Test]
        public void CreateCreatesDifferentInstances()
        {
            Assert.That(CreateFirstObject(), Is.Not.SameAs(CreateSecondObject()));
        }
        [Test]
        public void SameInstanceComparesEqual()
        {
            T o = CreateFirstObject();
            Assert.That(o, Is.EqualTo(o));
            Assert.That(o.GetHashCode(), Is.EqualTo(o.GetHashCode()));
        }

        [Test]
        public void Equivalence()
        {
            T o1 = CreateFirstObject();
            T o2 = CreateFirstObject();
            T o3 = CreateFirstObject();

            Assert.That(o2, Is.Not.SameAs(o1));
            Assert.That(o2, Is.Not.SameAs(o3));
            Assert.That(o3, Is.Not.SameAs(o1));


            Assert.That(o2, Is.EqualTo(o1));
            Assert.That(o2, Is.EqualTo(o3));
            Assert.That(o3, Is.EqualTo(o2));
        }
        [Test]
        public void EqualsIsCommutative()
        {
            T lhs = CreateFirstObject();
            T rhs = CreateFirstObject();

            Assert.That(lhs, Is.EqualTo(rhs));
            Assert.That(rhs, Is.EqualTo(lhs));
        }
        [Test]
        public void NonEquivalentInstancesDontCompareEqual()
        {
            T o1 = CreateFirstObject();
            T o2 = CreateSecondObject();
            Assert.That(o2, Is.Not.SameAs(o1));
            Assert.That(o2, Is.Not.EqualTo(o1));
            Assert.That(o2.GetHashCode(), Is.Not.EqualTo(o1.GetHashCode()));
        }
        [Test]
        public void GetHashcode()
        {
            T lhs = CreateFirstObject();
            T rhs = CreateFirstObject();
            Assert.That(lhs.GetHashCode(), Is.EqualTo(rhs.GetHashCode()));
        }
        [Test]
        public void GetHashcodeMultipleTimes()
        {
            T o = CreateFirstObject();
            Assert.That(o.GetHashCode(), Is.EqualTo(o.GetHashCode()));
        }
        [Test]
        public void GetHashcodeDiffersOnDifferentObjects()
        {
            T o1 = CreateFirstObject();
            T o2 = CreateSecondObject();
            Assert.That(o1.GetHashCode(), Is.Not.EqualTo(o2.GetHashCode()));
        }
    }
}